Mineralization and Magmatic activities of Indosinian-Yanshan Period in East Qinling Mountains

In the Mesozoic era, the tectonic system of the East Qinling Mountains undergone a major readjustment, from the south-north to the main tectonic stress field to the near-east-west to the main tectonic stress field. During this process,a large-scale delamination and thinning of the lithosphere resulted in intense indosinian-yanshanian magmatism. The main diagenetic age of Indosinian granitoids is Triassic, the diagenetic age is between 230 and 200 Ma, and the peak of granitic magmatism is 220 Ma ±; It shows the geochemical characteristics of I-type granite, and the magma source area is mainly crust source. The tectonic environment is related to the tectonic stress relaxation stage of the transformation from compression to extension tectonic system in the late period of the main collision orogeny in the Qinling Mountains. The main diagenetic age of Yanshanian granite is Early Jurassic and Early Cretaceous, the diagenetic age ranges between 200and 100 Ma, and the peak of granitic magmatism is 140 Ma ±; It shows the characteristics of transition from I-type to I-A type and then to A-type. The magma source area is characterized by mantle or crust mantle mixed source. The tectonic environment is related to the remote effect of the subduction of the Pacific plate to the Eurasian plate. The mineralization time limit of Early Mesozoic（Indosinian） granitoids in the East Qinling Mountains is between 230 and 200 Ma, and the mineralization peak is 210 Ma ±; The mineralization time limit of late Mesozoic（Yanshanian） granite is between 200～125 Ma, and the mineralization peak is 130 Ma ±. Indosinian mineralization and Yanshanian mineralization as a whole constituted the Mesozoic metallogenic explosion in the Qinling metallogenic belt, suggesting that the mineralization of endogenetic metal deposits in the East Qinling Mountains has the characteristics of multi period, multi stage and Mesozoic concentrated metallogenesis.